In overhead cranes of the type having rigid masts depending from an overhead support and an intermediate mast and load carriage vertically movable on the rigid mast, it is desirable to provide an operator's cab mounted directly on the intermediate mast or carriage. This arrangement provides the crane operator with a view of the carriage necessary for picking up, moving and depositing a load with the carriage. However, if there is a loss of load, i.e., a loss of vertical movement control over the intermediate mast and/or the carriage on which the load is supported, the operator's cab will drop downward out of control with the intermediate mast, the carriage and the load.
Previous solutions to this problem have included providing safety jaws to "catch" the load. Such a device would be, for example, mounted on the intermediate mast for clamping against a vertical intermediate mast guide rail on the rigid mast if an overspeed condition occurs. However, use of these mechanisms becomes quite difficult as the load size increases. Another solution that has been used is to provide a separate operator's cab mast so that the operator is isolated from the load. However, use of two separate masts increases the overall width of the crane and is quite expensive.